1. Field of the Invention
The present invention relates to a range (distance) image obtaining system which collects range image data of a region in the vicinity of a railway track while running along the railway track and inspects fastening devices, joint bars, track pads, etc.
2. Description of the Related Art
Rails in a railway are fixed at correct positions by fastening devices, joint bars, etc., to ensure safety in operation. The fastening devices of the rails are configured such that tip end portions of leaf springs press both sides of a base portion of the rail to secure the rails. Each leaf spring applies a pressing force by pressingly attaching its center portion onto a sleeper by means of a fastening bolt. If the rail fastening bolt gets loose, the tip end portion of the leaf spring could lift up from the base portion of the rail, causing the rail to be displaced laterally or a rail pad used for adjusting a height of the rail to be disengaged. This could possibly lead to a big accident. The joint bar is in contact with the side surfaces of the rails at abutted portions of their ends and is fastened to the rails by means of bolts to allow the rails to be joined together to provide continuity. Therefore, if the bolt gets loose, a joint portion of the rail is displaced and collides against a wheel, causing an abnormal vibration to be generated, or the wheel to be disengaged from the rail. This also could possibly lead to a big accident.
For the above stated reasons, it is necessary to inspect whether or not the fastening bolt and the joint-bar bolt are loose on a regular basis. Whether or not these bolts are loose is inspected by maintenance persons making the rounds for inspection in, for example, nighttime when running trains are fewer. The maintenance persons visually inspect whether or not the bolts are loose by visual observation or by hearing a sound made by hitting a driver. Under the circumstances, there is a need for a number of skillful maintenance persons, and there is a possibility that the loose of the bolts is overlooked because the inspection is performed by the persons. To solve this, an inspection system for monitoring the state of the fastening device and the state of the joint bar could possibly be incorporated into a railcar running along a track to detect their abnormalities, for the sake of convenience. Detecting the state of the rails on a daily basis by using an automatic inspection system is useful for preventive maintenance. In addition, the inspection performed by the maintenance persons who make the rounds is risky, and therefore it is expected that inspection is performed by the inspection system mounted to the railcar.
Japanese Laid-Open Patent Application Publication No. 2006-176071 discloses a track image analyzing system for determining a location of a sleeper. The track image analyzing system disclosed in Patent Literature 1 includes an image sensor positioned vertically above a fastening device in the vicinity of the rail, and a lamp for performing lighting with a vergence angle of 5 to 35 degrees with respect to an optical axis of an image sensor, to easily obtain a railway track image having a shade. The track image analyzing system disclosed in this publication is positioned under a floor of a track checking railcar and actuates an imaging device to obtain an image signal during high-speed running. An integrated value of a signal determined as an edge from an image output of the imaging device is calculated, and a region with a lower edge integrated value is identified as a surface of the sleeper. Thus, the location of the sleeper is determined. Furthermore, for each sleeper, it can be determined whether or not there is an abnormality in the fastening device, based on whether or not there is an edge in a location where the fastening device should be present
Japanese Laid-Open Patent Application Publication No. 2008-224631 discloses an inspection system mounted under a floor of a track checking railcar or the like, to inspect the degree to which rail fastening bolts of a railway are loose during running. The inspection system disclosed in this publication detects a spot laser applied to a head of the fastening bolt by a line sensor, and measures the height of the head of the fastening bolt based on a principle of triangulation, thereby detecting an abnormality of a tightening state of the bolt. Since the track checking railcar runs at a high speed of about 110 km/hr, the railcar moves up and down, and shakes in a horizontal direction. Therefore, a measurement location fluctuations, which is unavoidable. Furthermore, there are plural forms of a leaf spring which presses the rail, and therefore, a location of the fastening bolt changes depending on the kind of the leaf spring.
The inspection system disclosed in Japanese Laid-Open Patent Application Publication No. 2008-224631 evaluates the loose of the bolt correctly by measuring the height of the top head portion of a rail and calculating the height of the head portion of the bolt on the basis of the top head portion of the rail. In order to prevent a failure to detect the loose of the bolt due to lateral swaying of the railcar or incorrect positions of the fastening device, a plurality of spot laser projectors are arranged, and at least one of the spot laser projectors is adapted to emit the light to the bolt. The respective spot laser projectors are configured to emit light with a time difference so that a reference line of triangulation can be identified correctly.
In actuality, however the inspection system disclosed in Japanese Laid-Open Patent Application Publication No. 2006-176071 is utilized to determine a recorded image by visual inspection, because automatic inspection determination is difficult due to the fact that three-dimensional information is not obtained, the inspection system is significantly affected by contamination, rust, and others The inspection system disclosed in Japanese Laid-Open Patent Application Publication No. 2008-224631 has a problem that the spot laser projector can determine only the height of a target portion and cannot determine an abnormal state of a component such as the joint-bar bolt in a loose state, which is merely moved in a horizontal direction, and the height of the head of the bolt does not change. In addition, since a highest point of a component is detected based on only height information, it is difficult to identify this distinctively from a ballast, a cable disturbance, and others.